netdev - RE: [EXT] Re: [PATCH net-next] net: fec: Use a proper ID allocation scheme

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Date:   Tue, 18 Feb 2020 13:54:52 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Fabio Estevam <festevam@...il.com>
CC:     David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>
Subject: RE: [EXT] Re: [PATCH net-next] net: fec: Use a proper ID allocation
 scheme

From: Fabio Estevam <festevam@...il.com> Sent: Tuesday, February 18, 2020 9:25 PM
> Hi Andy,
> 
> On Tue, Feb 18, 2020 at 3:51 AM Andy Duan <fugang.duan@....com> wrote:
> 
> > > What about:
> > >
> > > 1) unbind fec0
> > > 2) unbind fec1
> > > 3) bind fec0
> > >
> > > It doesn't work even with the IDR scheme.
> >
> > Not only such case, instance#A (maybe fec0 or fec1) depends on
> > instance#B (maybe fec1 or fec0), Unbind instance#B firstly has problem.
> > Bind instance#A firstly also has problem.
> 
> Yes, I do see the error now with the sequence suggested by David.
> 
> I have also noticed in the fec_main.c comments:
> 
> /*
> * The i.MX28 dual fec interfaces are not equal.
> * Here are the differences:
> *
> *  - fec0 supports MII & RMII modes while fec1 only supports RMII
> *  - fec0 acts as the 1588 time master while fec1 is slave
> *  - external phys can only be configured by fec0
> *
> * That is to say fec1 can not work independently. It only works
> * when fec0 is working. The reason behind this design is that the
> * second interface is added primarily for Switch mode.
> *
> * Because of the last point above, both phys are attached on fec0
> * mdio interface in board design, and need to be configured by
> * fec0 mii_bus.
> */
> 
> Should we prevent unbind operation from this driver like this?
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index 4432a59904c7..1d348c5d0794 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -3793,6 +3793,7 @@ static struct platform_driver fec_driver = {
>                 .name   = DRIVER_NAME,
>                 .pm     = &fec_pm_ops,
>                 .of_match_table = fec_dt_ids,
> +               .suppress_bind_attrs = true
>         },
>         .id_table = fec_devtype,
>         .probe  = fec_probe,
> 
> Please advise.
> 
> Thanks

For imx6sl/imx8mp/imx8mm/imx8mn, soc only has one instance, bind operation
is supported and has no problem.

Regards,
Andy